Conventional internal combustion engines are well-known. Improvements of such engines naturally led to the development of the gas turbine engines. The principal advantage of the gas turbine engine is a favorable "grvity power index," i.e. weight to power (kg/km) ratio, which made such engines particularly adaptable to aircraft application.
On the other hand, the application of a gas turbine engine to land craft, such as an automobile, requires extensive use of expensive and bulky heat exchangers. This not only complicates the construction and increases the weight of the engine, but prohibitively increases the cost of such engines.
The maximum efficiency of the piston engines and the gas turbine is between 30% and 40%; the remaining chemical energy of the fuel is wasted.
Of major consequence is the large efficiency drop of a gas turbine under partial power utilization, and therefore is not preferably applicable to land crafts.